The invention relates to a connection device for fluid lines comprising a housing in which at least one housing recess is formed stepped in the longitudinal direction and merging at an inner end thereof with a fluid duct, an attachment means being fixed in the housing recess and defining a passage opening rendering possible the plugging into position of a fluid line, which is to be connected, such attachment means being provided with a sealing ring having an inner periphery matching the outline of the fluid line to be connected, such sealing ring furthermore having such connected fluid line extending through it, a centering section of the housing recess being located axially within the attachment means, into which centering section the end section of the connected fluid line extends with a simultaneous transverse supporting action.